A slide fastener stringer generally comprises a pair of coupling elements mounted upon respective stringer tapes and formed with interdigitatable coupling heads of a given spacing or pitch so that when a slider is moved along the stringer, the coupling elements are interconnected and when the slider is moved along the stringer in the opposite direction, the coupling elements are separated from one another.
The coupling elements can be continuous elements in the form of a coil or meander of a synthetic resin monofilament or can be rows of individual coupling heads which are mounted on the edge of the support tape, e.g. by clamping the individual coupling head onto the edge.
Other methods of affixing the coupling elements (this term being synonymous with the row of coupling heads) to the tape include fitting the coupling heads through openings in the tape, weaving or knitting the tape around the coupling elements, or stitching the coupling elements to the tape.
For separable slide fasteners, at one end of the stringer consisting of the two stringer halves, the slider and any end stop members which may be required, a plug and socket connection can be provided.
This plug and socket assembly can include a male member or pin element which can be inserted through the slider and into the female member or box element of the other stringer half to thereby position the two stringer halves at the end at which the slider is disposed to enable the slider to merge the coupling heads and secure the stringer halves together.
The stringer is generally produced in the form of a continuous tape or strip and can be formed with a T-shaped opening at the region at which the connecting elements are to be applied for facilitating the assembly of the slider onto the coupling elements as well as the mounting of the pin and box-connecting elements thereon. It will be appreciated that the region of this T-shaped cutout can be reinforced, e.g. by coating, cementing or otherwise applying reinforcing foil elements to the edges of the opening before or after the formation of the cutout. The connecting elements can be of the split-sleeve type which can be threaded onto the respective edges of the respective stringer halves and clamped thereon to close the slit around the fabric of the respective support tape.
In German patent document Open Application DE-OS No. 21 12 076, the corresponding U.S. Pat. No. 3,714,698 and the corresponding British Pat. No. 1,337,334, there is described a machine and automatic mounting of connection elements adapted to form a plug and socket connection for a separable slide fastener. With this machine, the two stringer halves are separated and the edge at which the box and pin elements are to be applied lie in the plane of the stringer so that the mounting for threading onto the box and pin elements onto the respective edges can also be in this plane.
This system requires a complex mechanism because of the complicated control techniques which are required and may not always be reliable because of tolerance variations which may cause relative shifting of the stringer halves. This can result in defective slide fastener stringers.